Ramón Balsa

The effect of soil moisture on soil microbial activity studied by microcalorimetry

Abstract Microcalorimetry has been used to study the effect of moisture on soil microbial activity. Different moisture regimes produce changes on heat flow rate-time curves recorded for soil samples, affecting also certain parameters, such as the total heat evolution Q tot , the microbial growth rate constant μ and growth yield Y , which are calculated by the microcalorimetric method. A positive correlation was found between the percentage humidity, the total heat evolution and the microbial growth rate constant. The values of these parameters decrease with the dryness of the soil. Field capacity moisture appears to be the optimum moisture level for soil microbial activity.

Comparative study of the microbial activity in different soils by the microcalorimetric method

Abstract Microcalorimetry was applied to the study of the microbial activity of four soils with different percentages of organic matter. The qualitative study of the heat flow rate-time curves, recorded from soil samples amended with glucose, showed remarkable differences in the soil microbial activity. In order to show results in a more quantitative way, the total heat evolution, Q tot , the total heat evolution of soil samples amended with glucose, Q tot(glc.) , and the values of peak time and microbial growth rate constant, μ, were calculated from the heat flow rate-time curves recorded from all samples. Values of peak time increased with decreased microbial density and a positive correlation between total heat evolution, Q tot , and percentage of organic matter, was found. Microcalorimetry appears as a suitable technique to carry out both qualitative and quantitative comparative studies of microbial activity in soils.

Context effects in the auditory identification of Spanish fricatives /f/ and /θ/: Hyper and Hypospeech

Twenty‐eight subjects heard 40 Spanish words in which the initial fricative was /f/ or /θ/, combined with vowels /e/ and /u/. Ten words were used for each particular combination (2 fricatives×2 vowels ×10 words). Two forms of speech (Hypo and Hyperspeech) and four conditions were considered: (1) Isolated fricative segment; (2) fricative segment + 51.2 ms of the following vowel; (3) fricative + whole following vowel; (4) whole word. The statistical analysis showed that, despite their differences in production and acoustic characteristics, isolated fricative segments were equally recognized in Hypo and Hyperspeech (cond. 1). Including the vowel ( conditions 2 and 3) significantly improved recognition of both fricatives for both forms of speech, except for the combination /f/+/e/: While fricative identification improves slightly in Hyperspeech, in Hypospeech, recognition decreases with respect to cond. (1). For this particular combination, an acceptable recognition rate is only achieved in the whole word con...

Perceptual effects of coarticulation in fricatives

The perceptual interaction between the consonant and the vowel in fricative+vowel syllables is evaluated. A set of conflicting cue stimuli was used to measure the relative importance of: (a) the influence of the vowel in the previous consonant, and (b) the influence of the fricative in the following vowel. It is concluded that the perceptual interaction between the consonant and the vowel in fricative-vowel syllables can not be explained only by the coarticulatory influence of the consonant or vowel on adjacent segments. The influence of the vowel in the previous fricative is perceptually irrelevant, while the influence of the fricative in the following vowel is more important for the identification of //spl theta// and /f/ than for /s/ and //spl int//. Actually it is perceptually irrelevant for //spl int// and a little important for /s/. Besides the influence of the fricative in the following vowel is notably dependent on the particular vowel.

Influence of frequency range in the perceptual recognition of fricatives

The objective of this paper is to study the importance of various frequency bands for the identification of fricatives. Tokens were CV syllables formed by the combination of the Galician fricatives /θ,f,s,∫/ and the vowels /a,e,i,o,u/ which were pronounced in Hyperspeech form by a man and a woman. Tokens were sampled at 32 kHz and low‐pass filtered with cutoff frequencies of 11, 8, 5.5, 4, and 3 kHz. Thus, the total number of tokens was 240=4 fricatives× 5 vowels× 2 sexes× 6 frequencies. Thirty‐seven listeners carried out the perceptual experiments in two conditions: (1) whole fricative noise plus 100 ms of the following vowel, and (2) whole fricative noise. The results of the perceptual experiments show that as the cutoff frequency is lowered, (a) /s/ tends to be recognized as /θ/ in both conditions; (b) the fricative noise of /θ/ tends to be recognized as /f/, and (c) recognition of /f/ and /∫/ is affected to a lesser extent. Results suggest the importance of low‐frequency energy in the characterization...

Recognition of Portuguese vowels by Galician‐speaking and Spanish‐speaking listeners

Galician, Portuguese, and Spanish are three romanic languages spoken in the Iberian peninsula. Galician and Portuguese are historically related and keep the same vocalic system of common latin: a, e, e, i, ɔ, o, u. In Spanish the number of vowels was reduced to five: a, e, i, o, u. Nevertheless, Spanish has exerted considerable influence on Galician, contributing to weaken the vocalic contrasts e–e and ɔ–o. The purpose of these experiments was to assess how Galician‐ and Spanish‐speaking listeners perceived the vocalic system of Portuguese. Stimuli were pV syllables pronounced in a carrier phrase, where V was one of the seven vowels. Results show that Galician‐speaking listeners have some difficulty in perceiving the contrasts e–e and ɔ–o, probably due to the historical influence of Spanish, and despite the fact that F1 and F2 of the Portuguese vowels were similar to those reported for Galician vowels. Spanish‐speaking listeners identified e–e as a single vowel e, and ɔ–o as a single vowel o, associating ...

Integration of acoustic cues in Spanish voiced stops

In Spanish, voiced stops in initial position usually show the presence of a voice bar before the release burst. In this study, the perception of word‐initial voiced stops when the voice bar is removed is examined. Nine men and nine women pronounced 15 Spanish words in which the initial consonant was /b/, /d/, or /g/ in combination with the vowels /a/, /e/, /i/, /o/, /u/. Seventeen subjects with normal hearing heard the stops in two conditions: (1) whole voice bar + 102.4 ms of signal from burst onset; (2) 102.4 ms from burst onset. In condition (2), tokens were perceived as the correct stop, as its voiceless counterpart, or as an ambiguous signal. Removing the voice bar caused 37% of /b/ tokens to be classified as /p/; 41% of /d/s to be classified as /t/s ; and 19% of /g/s to be classified as /k/s. The change in voicing characteristics was significantly more marked for women. The results indicate that the integration of the voice bar with the burst and the vowel plays a relevant role in the perception of voicing in voiced stops, especially in women’s speech, smoothing the dynamic frequency characteristics of burst and vowel.